1. Field of the Invention
The present invention relates to an electronic component and a method for manufacturing the electronic component and, in particular, to an electronic component including a portion in which a plating layer is disposed in a pad opening of an insulating layer located on a substrate and an external terminal is disposed on the plating layer, and a method for manufacturing the electronic component.
2. Description of the Related Art
In general, in order to manufacture an elastic wave device included in an elastic wave apparatus, a plurality of elastic wave devices are manufactured in the form of a mother substrate and, subsequently, the mother substrate is separated into separate components each defining an elastic wave device.
For example, FIG. 26A is a plan view schematically illustrating the manufacturing steps of a boundary elastic wave apparatus. FIG. 26B and FIGS. 27A to 27D are cross-sectional views taken along a line P-P of FIG. 26A and illustrate the manufacturing steps of the boundary elastic wave apparatus.
As shown in FIG. 27A, a comb-shaped IDT (interdigital transducer) electrode 9 that defines a boundary elastic wave device, which is one type of an elastic wave device, and an interconnection line 12 are formed on a piezoelectric substrate 1 using a first electrode layer. Thereafter, an insulating film 7 is formed on the first electrode layer. After an opening for exposing a portion of the interconnection line 12 (a bump) is formed in the insulating film 7, an under bump metal underlayer 13 and power supply lines 2 (not shown in FIGS. 27A-27D), 3, and connected to the under bump metal underlayer 13 are formed using a second electrode layer. As shown in FIG. 26A, the power supply lines 2, 3, and 14 include portions that are formed so as to surround the entire periphery of a component that defines a boundary elastic wave device in strip-shaped dicing areas 2A and 3A indicated by dotted lines. The dicing areas 2A and 3A are removed from the mother substrate in a dicing step performed later. Thus, the dicing areas 2A and 3A do not remain in the component defining a boundary elastic device.
Subsequently, as shown in FIG. 27B, a sound-absorbing film 8 is formed on the insulating film 7 using an insulating material. Thereafter, as shown in FIG. 27C, an opening 8a for exposing the under bump metal underlayer 13 is formed in the sound-absorbing film 8.
Thereafter, electrolytic plating is performed while power is being applied to the power supply lines 2, 3, and 14. Thus, as indicated by FIG. 27D, a plating layer 15 that serves as an under bump metal is formed on the under bump metal underlayer 13. Subsequently, as indicated by FIG. 26B, a metal bump 11a that serves as an external terminal is formed on the plating layer 15.
Subsequently, the dicing areas 2A and 3A are scraped off using a dicing blade so that the component defining a boundary elastic wave device is formed. Through such a dicing step, a side surface 6a of the component defining the boundary elastic wave device is formed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2007-28195). However, when the power supply line is continuously formed in the dicing area so as to surround the entire periphery of a component defining an elastic wave device, the following problems arise.
If the power supply line that surrounds the entire periphery of a component defining an elastic wave device remains in the component after a dicing operation is performed, a short circuit in the device is caused. Thus, operational malfunction occurs. In order to prevent this problem, the power supply line that surrounds the entire periphery of a component defining an elastic wave device must be formed so as not to extend beyond the dicing area. That is, the width of the power supply line must be less than the width of the dicing area.
On the other hand, in an electrolytic plating process, plating is formed so as to be thicker towards a portion to which external electrical charge is supplied and thinner towards a direction away from the portion due to the electrical resistance of the power supply line. In order to reduce non-uniformity of the thickness of the plating or in order to increase the plating speed, the width of the power supply line must be increased. However, in such a case, the width of the dicing area must be increased to a value greater than or equal to the width of the power supply line in order to prevent a short circuit from occurring in the elastic wave device. If the width of the dicing area is increased, the number of components defining elastic wave devices obtained by separating a mother substrate having the same dimensions is decreased. Thus, the efficiency of the production is decreased.
As indicated by the cross-sectional view in FIG. 24A, if the insulating layer 30 that is formed on the piezoelectric substrate 2 is also formed on a power supply line 21 in the dicing area indicated by dotted lines in order to prevent formation of plating on the power supply line 21, the insulating layer 30 formed in the dicing area must be removed in the dicing step, as indicated by the cross-sectional view in FIG. 24B. Removal of the insulating layer reduces the life of the dicing blade, and the dicing speed cannot be increased.
As indicated by the cross-sectional view in FIG. 25A, the power supply line 21 having a width B and surrounding a component defining an elastic wave device is formed on the piezoelectric substrate 2. In addition, as indicated by the cross-sectional view in FIG. 25B, in order to expose the power supply line 21, the boundary opening 38 is formed in the insulating layer 30 formed on the piezoelectric substrate 2. Furthermore, a slope 39 is formed in the insulating layer 30 in the vicinity of the boundary opening 38. In such a case, as indicated by the cross-sectional views in FIGS. 25C-1 and 25C-2, a plating layer 90 to be formed on the power supply line 21 that is exposed through the boundary opening 38 in the insulating layer 30 is formed so as to expand along the slope 39 in the vicinity of the boundary opening 38 in the insulating layer 30. Thus, a width C of the plating layer 90 is greater than a width B of the power supply line 21 shown in FIG. 25A.
As shown in FIG. 25C-1, if a width W1 of the dicing area is less than the width C of the plating layer 90, a portion 92 of the plating layer 90 remains on the periphery of the component defining an elastic wave device even when the power supply line 21 in the dicing area is completely removed, as shown by the cross-sectional view in FIG. 25D-1. Thus, a short circuit in the elastic wave device occurs. If, as shown in FIG. 25C-2, if a width W2 of the dicing area is greater than the width C of the plating layer 90, the plating layer 90 can be completely removed by dicing, as shown in FIG. 25D-2.
As described above, in order to completely remove the plating layer 90, an area having a width greater than the width C of the plating layer 90 must be removed. Accordingly, it is difficult to increase the efficiency of production by increasing the number of components defining elastic wave devices obtained by separating a mother substrate having a constant size.
In addition, in recent years, one type of laser dicing method called “stealth dicing” has been used. In the stealth dicing method, a laser beam having a wavelength that passes through a dicing area is emitted and is focused on a point inside the substrate. In this way, a crack is generated inside the substrate. Thereafter, the substrate is expanded so that the substrate is separated. However, if the power supply line and the insulating layer are present in the dicing area and, therefore, the piezoelectric substrate is not exposed, a laser beam emitted from the outside does not reach the inside of the piezoelectric substrate. Consequently, the stealth dicing method cannot be applied.